Structure of N,N'-bis(amino acids) in the solid state and in solution. A 13C and 15N CPMAS NMR study

Three bis(amino acids) linked by the amino groups have been prepared and structurally characterized. We have named them Gly-Gly, Ala-Ala and Gly-Ala (or Ala-Gly). These compounds have been characterized by NMR both in solution and in the solid state. They exist as zwitterions with the ammonium group proximal to the carboxylate anion. In the case of Gly-Ala, a dynamic situation is observed by CPMAS NMR ((13)C and (15)N) corresponding to a double proton migration between two proximal tautomers.